The present disclosure relates generally to semiconductor manufacturing. Specifically, the present disclosure relates to systems and methods that provide proximity effect correction for electron beam writing.
Electron-beam (or “e-beam”) writing relates to a process for creating changes in a medium using e-beams. Specifically, some e-beam processes use e-beams to write designs onto mediums. Examples of mediums that can be written on with e-beams include semiconductor wafers and photomasks (e.g., fused silica and chrome masks). E-beam writing provides a way to create features on a medium where the features are smaller than a resolution limit for light.
However, as feature sizes shrink, behaviors of e-beams, such as forward scatter and back scatter phenomena, become more significant. As a result of scattering phenomena, a shape actually written to a medium may differ somewhat from the pattern of the pixels written by the e-beam. This is also referred to as the proximity effect. Conventional methods correct for the proximity effect by adding alterations such as serifs or hammerheads to the pixel pattern so that the resulting shape is closer to the desired design feature. Other conventional methods use a pixel-by-pixel dosage modulation process, where dosage of a pixel is equal to beam intensity multiplied by exposure time. The dosage at each pixel can be set to make the resulting shape closer to the desired shape. In an example of a conventional process, a pixel map is provided to a mathematical modeling system that predicts how the resulting shape would appear upon inspection of the medium. The model is then compared to the desired shape to produce an error. The error is minimized by use of shape correction or pixel-by-pixel dosage modulation.
The above-described conventional techniques have some disadvantages. For instance, shape correction by itself may not provide sufficient correction for very fine features. Also, pixel-by-pixel dosage modulation requires much processing power because of the large number of pixels that may be present in a given design. More efficient and effective proximity effect correction is called for.